Appearing on a roundtable discussion on NBC's "Meet the Press," Booker, an Obama supporter, described as "nauseating" the ad released last week about Bain's involvement with a Kansas City steel company that later went bankrupt.

"I have to just say from a very personal level, I'm not about to sit here and indict private equity," Booker said.

"If you look at the totality of Bain Capital's record, they've done a lot to support businesses, to grow businesses," he added. "And this, to me, I'm very uncomfortable."

Booker did say he believes the Obama administration's policies have benefited "average Americans" and small businesses.

But the ad leveled at Bain Capital are "nauseating," although he also criticized Republicans for attacks like the ones on Obama's controversial former pastor, Jeremiah Wright.

"This kind of stuff is nauseating to me on both sides," Booker said. "It's nauseating to the American public. Enough is enough. Stop attacking private equity. Stop attacking Jeremiah Wright. This stuff has got to stop, because what it does is it undermines, to me, what this country should be focused on. It's a distraction from the real issues."

"It's either gonna be a small campaign about this crap, or it's gonna be a big campaign in my opinion about the issues the American public cares about," he said.

"I'll always prioritize my nation over a political party. (And) right now crass divisive partisan politics is not serving the citizens of my city," he wrote later on Twitter.

"So I'll clarify my comments on (Meet the Press)," he added. "Yes, Obama must be re-elected. But we as a nation owe it to him (and) ourselves (to) reject politics as usual."